Titanium material having coating layer at its surface laminated glass including the same and process for producing them

ABSTRACT

The titanium materials of the present invention have an oxide film on the surface and an interference color of the oxide film. In forming a transparent coating layer on the surface of the titanium materials, provisions are made so that the oxide film has an thickness of 150 nm to 600 nm, or the interference color due to the anodic oxide film is developed by the actions of both wavelengths strengthened and weakened by interference and the color phases of the color developed by the wavelength strengthened by interference and that of complementary colors of the color developed by the wavelength weakened by interference are as close to each as not more than 90 degrees apart on the color wheel, or the L* value on the L*a*b* calorimetric system is not less than 33. The laminated glasses of the present invention having excellent ornamentality comprise at least said titanium sheet interposed between multiple sheet glasses layered together by means of adhesive layers.

TECHNICAL FIELD

This invention relates to titanium materials with a surface-coatinglayer and their manufacturing methods and, more particularly, totitanium materials, whose surfaces are colored by the interferenceaction of oxide films, are covered with a transparent coating layer toprevent discoloration, and manufacturing methods thereof. This inventionalso relates to laminated glass, comprising a titanium sheet sandwichedbetween sheet glasses and having excellent ornamentality, andmanufacturing methods thereof.

BACKGROUND TECHNOLOGY

Titanium, that exhibits very high corrosion resistance in theatmosphere, is used in building applications such as roofs and walls inseacoast areas. Although more than ten years have passed since titaniumbegan to be used for roofs and other building materials, no cases ofcorrosion have ever been reported. However, the surface of titanium,depending on service environment, sometimes becomes a dark golden colorduring long use.

Though this discoloration is limited to the very shallow surface and,therefore, does not impair the anti-corrosive function of titanium, itsometimes gives rise to problems when titanium materials colored byinterference color are used for their ornamentality.

Because of their ornamentality, titanium materials colored by theinterference color are also used in applications other than outdoorones. Because coloring is based on the interference action of oxidefilms, smudging with finger prints or oily stains makes the smudged partappear to have a different color tone and is noticeable.

To prevent the environment-dependent discoloration mentioned first,Japanese Unexamined Patent Publication 130886 of 1998, for example,discloses a method to prevent discoloration of titanium materials byspecifying the structure of oxide films on them.

“Surface Treating Measures Q and A 1000” compiled by the SurfaceTreating Measures Q and A 1000 Editorial Committee (page 634, publishedby Sangyo Gijutsu Service Center Co., Ltd. In May 1998) depicts a methodto prevent surface discoloration, deterioration and contamination byapplying transparent coatings. However, this document also says that“this method sacrifices the color of interference coating in preventingcontamination and, therefore, no methods to prevent surfacecontamination without losing the color of interference coating have everbeen established.” Contamination can be also prevented by sandwiching atitanium sheet between sheet glasses by way of adhesive layers. However,the surface of titanium sheets sandwiched between sheet glasses aresimilar to that of titanium sheets covered with transparent coating.Therefore, the interference color is impaired as in the case of titaniumsheets covered with a transparent coating.

Laminated glasses are manufactured by inserting one or more strongtransparent synthetic resin films between two or more sheet glasses,with application of heat and pressure. When laminated glasses break, thestrong synthetic resin film prevents shattering of glass and providessafety. When laminated glasses are hit, the strong synthetic resin filmsdo not allow the penetration of the hitting object and, thus, proveeffective in crime prevention. Because of these advantages, laminatedglasses are widely used for windows, doors and other applications inautomobiles and other transportation facilities and buildings.

Laminated glasses sandwiching sheets of paper or cloth or metal foilsbetween two or more sheet glasses to enhance ornamentality are alsoproposed (as in, for example, Japanese Unexamined Patent Publication12456 of 2002 and Japanese Unexamined Utility Model Publication 47339 of1994). Inserting sheets of paper or cloth or metal foils between sheetglasses provide higher ornamentality to laminated glasses by permittingthe degree of transparency (including semitransparency and opaqueness),color and pattern to be variously altered depending on use.

Titanium is used for roofs, walls and other building materials incoastal regions as they exhibit very excellent corrosion resistance inthe atmospheric environment and titanium colored by the interferencecolor has high ornamentality because of the vivid colors that changewith the angle of view. Although more than ten years have passed sincetitanium began to be used for roofs and other building materials, nocases of corrosion have ever been reported. However, the surface oftitanium, depending on service environment, sometimes becomes a darkgolden color during long use.

DISCLOSURE OF THE INVENTION

An object of this invention is to provide titanium materials, colored bythe interference color and with excellent ornamentality, that have asurface coating layer to prevent discoloration due to the deteriorationof the oxide film and color changes due to smudges on the surfaceoccurring use as roofs, walls and other building materials inatmospheric environments and methods of manufacturing the same.

Another object of this invention is to provide laminated glasses havinggreater ornamentality than conventional ones by permitting preservationof the beautiful appearance characteristic of titanium sheets andmethods of manufacturing the same.

The present invention aims at protecting the surface of titaniummaterials colored by the interference color without impairing theornamentality thereof. The inventor discovered that provision of atransparent coating layer does not impair the interference color byappropriately controlling the thickness of oxide film, the coloringmechanism of interference color and the lightness in color of basesheets. The inventor also discovered that laminated glasses, making themost of the beautiful appearance characteristic of titanium sheets, canbe manufactured. The gist of the present invention, that was completedbased on these findings, is as follows:

-   -   (1) A titanium material having an oxide film with an        interference color formed on the surface thereof and covered        with a transparent coating layer, characterized in that said        oxide film has a thickness of 150 to 600 mm.    -   (2) A titanium material having an oxide film with an        interference color formed on the surface thereof whose        interference color is developed by the action of a wavelength        strengthened by interference and a wavelength weakened by        interference and covered with a transparent coating layer,        characterized in that the color phases of the color developed by        the wavelength strengthened by interference and that of        complementary colors of the color developed by the wavelength        weakened by interference are as close to each other as not more        than 90 degrees apart on the color wheel.    -   (3) A titanium material having a coating layer on the surface        thereof described in (1), characterized in that the color phases        of the color developed by the wavelength strengthened by        interference and that of complementary colors of the color        developed by the wavelength weakened by interference are as        close to each other as not more than 90 degrees apart on the        color wheel.    -   (4) A titanium material having a coating layer on the surface        thereof, characterized in that the titanium material whose        lightness in color before the formation of the coating layer is        not less than 33 in terms of the L* value on the L*a*b*        colorimetric system based on JIS Z 8730.    -   (5) A titanium material having a coating layer on the surface        thereof described in any of (1) to (3), characterized in that        the titanium material whose lightness in color before the        formation of the coating layer is not less than 33 in terms of        the L* value on the L*a*b* calorimetric system based on JIS Z        8730.    -   (6) A titanium material having a coating layer on the surface        thereof described in any of (1) to (5), characterized in that        said oxide film is covered with an alkali titanate layer.    -   (7) A titanium material having a coating layer on the surface        thereof described in any of (1) to (5), characterized in that        said oxide film is covered with an alkali titanate layer.    -   (8) A titanium material having a coating layer on the surface        thereof described in any of (1) to (7), characterized in that        said transparent coating layer is a clear paint film.    -   (9) A titanium material having a coating layer on the surface        thereof described in any of (1) to (7), characterized in that        said transparent coating layer is a layer of adhesive.    -   (10) A laminated glass comprising multiple sheet glasses layered        together by means of an adhesive layer with the titanium        material described in any of (1) and (7) interlayered between        said sheet glasses by way of said layer of adhesive.    -   (11) A laminated glass described in (10) in which said titanium        materials have openings of 1 to 90 percent in said titanium        materials.    -   (12) A laminated glass described in (10) in which the light        transmittance of said layer of adhesive at the wavelength        between 100 and 390 nm is not greater than 1 percent.    -   (13) A laminated glass described in (10) or (11) in which said        layer of adhesive is a hot melt adhesive.    -   (14) A method for manufacturing the titanium material having a        coating layer on the surface thereof described in any of (1)        to (9) comprising the steps of forming an oxide film on the        surface of a titanium material, treating in an alkaline        solution, and covering the surface with a transparent coating        layer.    -   (15) A method for manufacturing the titanium material having a        coating layer on the surface thereof described in (14) in which        the pH of said alkaline solution is not lower than 8 and not        higher than 14 and the treatment temperature is not lower than        10° C. and not higher than 90° C.    -   (16) A method for manufacturing the laminated glass described in        any of (10) to (13) comprising the steps of forming an oxide        film on the surface of a titanium sheet, treating in an alkaline        solution, and lamination the titanium sheet and sheet glasses        through an adhesive layer.    -   (17) A method for manufacturing the laminated glass described        in (16) in which the pH of said alkaline solution is not lower        than 8 and not higher than 14 and the treatment temperature is        not lower than 10° C. and not higher than 90° C.    -   (18) A method for manufacturing the laminated glass described        in (16) or (17) in which the layer of adhesive is sheet-formed        and the sheet glasses, sheet-formed adhesive and titanium sheet        are layered together in the desired order and laminated together        by hot press lamination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram to show the measurement of the thickness of theoxide film or the layer of alkali titanate by Auger electronspectroscopy.

FIG. 2 shows the general structure of a laminated glass with aninterlayer of a titanium sheet according to this invention.

FIG. 3 shows how the sheet glasses, sheet-formed adhesive and titaniumsheet are layered together in manufacturing a laminated glass.

FIG. 4 shows a laminated glass with an interlayer of a titanium sheetnot having apertures.

FIG. 5 shows a laminated glass with an interlayer of a titanium sheethaving apertures.

PREFERRED EMBODIMENTS OF THE INVENTION

While the oxide film on the surface can be prepared either by anodicoxidation in an electrolyte or chemical oxidation in a solutioncontaining hydrogen peroxide or a strong acid or a strong alkalinesolution, anodic oxidation with the titanium material acting as theanode is preferable because it easily provides uniform color. While theelectrolyte solution is not particularly limited, a solution containingphosphoric acid, sulfuric acid, boric acid or one or more salts of saidacids is generally used. The desired color is developed by acommercially used method that controls the voltage applied to thetitanium material. An oxidation process using a combination ofhydrofluoric acid with nitric acid or an oxidizing agent such asoxygenated water can be added before the anodic oxidation process forthe removal of contamination from the surface of base titanium sheet orto the control of the surface luster thereof.

The thickness of the oxide film formed on the surface should preferablybe not smaller than 150 nm and not greater than 600 nm. If the thicknessis smaller than 150 nm, the interference color is sometimessignificantly impaired on formation of the coating layer. To leave amore vivid interference color after the formation of the transparentcoating layer, thicker oxide films are preferable. Forming an oxide filmnot smaller than 200 nm in thickness is conducive to leaving a morevivid interference color. If, however, the thickness of the oxide filmexceeds 600 nm, the interference color disappears before the coatinglayer is formed. Therefore, the thickness of the oxide film shouldpreferably be between 200 and 600 nm.

The thickness of the oxide film can be determined by Auger electronspectroscopy. With a 1 mass percent phosphoric acid solution and SUS 304stainless steel serving as the electrolyte solution and cathode, anoxide film with a thickness of 150 to 600 nm is obtained by applyingconstant voltage electrolysis at approximately 30 to 140 V. Therelationship between electrolysis voltage and film thickness variesbecause solution resistance varies with the bath composition and theposition of the cathode in the electrolyte solution and hydrogengeneration voltage varies with the type of the cathode.

The interference color developed by the oxide film is due to the actionof wavelengths both strengthened and weakened by interference. The colorphase of the color developed by the wavelength strengthened byinterference and that of complementary colors of the color developedcolors of the wavelength weakened by interference should be as close toeach other as not more than 90 degrees apart on the color wheel.

When only the wavelength corresponding to the color developed byinterference is strengthened, or when only the wavelength correspondingto the complementary color of the developed color is weakened, or whenthe color phases of the color corresponding to the wavelengthstrengthened by interference and the color corresponding to thewavelength weakened by interference are as close as not more than 90degrees away from each other on the color wheel, formation of atransparent coating layer on the surface sometimes significantly impairsthe interference color. If, however, the interference color is developedby the actions of wavelengths both strengthened and weakened byinterference and the color phases of the color developed by thewavelength strengthened by interference and that of complementary colorsof the color developed by the wavelength weakened by interference are asclose to each other as not more than 90 degrees apart on the colorwheel, formation of a transparent coating layer on the surface does notimpair the interference color because of the combined effect thereof.

When there are at least one each of wavelengths strengthened andweakened by interference in the wavelength range of 360 to 800 nmcorresponding to visible light, formation of a transparent coating layeron the surface does not impair the interference color if the colorphases of the color developed by additive mixing the colorscorresponding to one or more wavelengths strengthened by interferenceand that of the complementary colors of the color developed by additivemixing the colors corresponding to one or more wavelengths weakened byinterference are not more than 90 degrees away on the color wheelbecause of the combined effect thereof. However, when five or morewavelengths strengthened and weakened by interference exist in thevisible light wavelength range of 400 to 760 nm corresponding torelatively vivid colors, no vivid interference color appears before thecoating layer is formed because the effects of such colors are mutuallycancelled.

When a titanium material is colored by anodic oxidation, severalrotations are made on the color wheel through different gradations ofchroma and lightness as the coloring voltage and oxide film thicknessare increased until they converge to a low chroma color. Formation of anoxide film first develops yellow and then blue. Color developmentcontinues in the order or yellow and blue, followed by green, pink andother colors. Here, the yellow appearing first is called yellow of thefirst round, the blue appearing next blue of the first round, the yellowappearing next yellow of the second round, the blue appearing next blueof the second round, and the green appearing next green of the secondround.

The yellow and blue of the first round appear when only the wavelengthcorresponding to the developed color, only the wavelength correspondingto the complementary color of the developed color, or the color phasesof colors corresponding to the wavelengths strengthened and weakened byinterference are as close as not more than 90 degrees apart on the colorwheel. Therefore, formation of a transparent coating layer on thesurface significantly impairs the interference color. Incidentally, theyellow of the first round is developed by weakening by interference ofonly the wavelength corresponding to blue that is the complementarycolor of yellow. The darker blue of the first round appearing in theearly stage is developed by weakening by interference of only thewavelength corresponding to yellow that is the complementary colorthereof, whereas the lighter blue appearing subsequently is developed bystrengthening by interference of only the wavelength corresponding toblue and, at the same time, by weakening by interference the wavelengthcorresponding to purple that is close to blue.

In comparison, the yellow and blue of the second round are developed bythe action of both wavelengths strengthened and weakened byinterference. To be more specific, the yellow and blue of the secondround are developed by the combined effect of the color phases of thecolor corresponding to the wavelength strengthened by interference andthe complementary color of the color corresponding to the wavelengthweakened by interference that are not more than 90 degrees apart on thecolor wheel. Therefore, formation of the transparent coating layer doesnot erase the interference color. Incidentally, the yellow of the secondround develops when interference strengthens the wavelengthcorresponding to yellow and weakens the wavelength corresponding to bluethat is the complementary color of yellow. The blue of the second rounddevelops when interference strengthens the wavelength corresponding toblue and weakens the wavelength corresponding to yellow that is thecomplementary color of blue.

The green of the second round develops when there are one wavelengthstrengthened by interference and two wavelengths weakened byinterference in the wavelength range of 360 to 800 nm that correspondsto visible light. The color phases of the color corresponding to thestrengthened wavelength and the complementary color of the colorobtained by adding and mixing the colors corresponding to the twoweakened wavelengths are not more than 90 degrees apart on the colorwheel and the combined effect thereof develops the green of the secondround. Thus, formation of the transparent coating layer does not erasethe interference color. Incidentally, the green of the second rounddevelops when interference strengthens the wavelength corresponding togreen and weakens the wavelengths corresponding to red and purple.

The color of titanium materials having colors developed by theinterference color of the oxide film formed on the surface thereof byanodic oxidation in an electrolyte solution can be expressed by the L*value of the L*a*b* colorimetric system based on JIS Z 8730. The L*value should preferably be not lower than 33. If the L* value is lowerthan 33, formation of the coating layer sometimes impairs theinterference color.

When formation of the transparent coating layer erases the interferencecolor, the color of the surface changes to a color close to gray.Lighter colors with higher L* values are less susceptible to theinfluence of the coating layer.

Though not particularly limited, the thickness of the transparentcoating layer formed on the surface should preferably be not less than0.5 μm. If the thickness is smaller than 0.5 μm, the transparent coatinglayer itself sometimes possesses an interference effect that cancels theinterference color caused by the oxide film, makes it difficult tosecure uniformity of coating and causes color heterogeneity on thesurface. Though thicker coating layers do not produce any particularproblems so far as transparency is maintained, a thickness not more than2 mm is sufficient from the viewpoint of cost efficiency except in caseswhere, for example, surface irregularities must be absorbed.

In forming a transparent coating layer on the titanium material coloredby the interference color of the oxide film formed on the surfacethereof by anodic oxidation in an electrolyte solution, it is preferableto pretreat in an alkaline solution.

Sodium hydroxide, potassium hydroxide, lithium hydroxide, carbonate,metasilicate, orthometasilicate, phosphate, pyrophosphate,condensation-polymerized phosphate hydrochloride, bicarbonate andsurface-active agent can be used as the primary constituent of alkalinesolutions.

The pretreatment should be done in an alkaline solution whose pH is notlower than 8 and not higher than 14 and at a temperature not lower than10° C. and not lower than 90° C. It is more preferable, depending on thecomposition and the way of use of the alkaline solution, that thetemperature is not lower than 35° C. and not higher than 80° C. and thepH is not lower than 9 and not higher than 13.5. In this range, thedesired effect is obtained in several tens of seconds to a few minutes.If the temperature and pH are lower, there are possibilities thatadequate treatment takes long time and adequate effect cannot beobtained even if much time is spent. If the temperature and pH arehigher, there are possibilities that, depending on the treatment time,the oxide film is damaged to cause a change in the interference colorand equipment problems, such as the corrosion resistance of the alkalinebath vessel, arise.

Application of said treatment in the alkaline solution to the titaniummaterial colored by the interference of the oxide film formed on thesurface thereof by anodic oxidation in an electrolyte solution forms alayer of alkaline titanate on the surface of the oxide film thatincreases adherence between the titanium material and coating layer.Though not particularly limited, the alkaline titanate layer formed bythe treatment in said alkaline solution is approximately 0.5 to 10 nm inthickness. The alkaline titanate layer does not affect the interferencecolor if the thickness thereof is between approximately 0.5 to 10 nm.The thickness of the alkaline titanate layer can be determined by Augerelectron spectroscopy.

Examples of alkaline titanates, depending on the alkaline solution usedin the treatment, include sodium titanate, potassium titanate andlithium titanate.

Treatment in alkaline solutions is also usable for cleaning of titaniummaterials. The titanium oxide layer formed by anodic oxidation is porousand, therefore, intrinsically possesses a certain degree of adhesivenesswith the coating layer due to the anchor effect. As, however, thetitanium oxide formed by anodic oxidation is apt to adsorb smudges, goodadhesiveness with the coating layer is difficult to obtain unless keptin environments that retard contamination immediately after anodicoxidation. When, however, titanium materials are transported orsubjected to pressing, punching or other similar operations, oil or aprotective film is often applied to prevent surface damages. Residualoils and residual phosphate esters or other release agents or adhesivesfrom protective films, even if invisible, often adversely affect theadhesiveness with the coating layer. Therefore, another treatment isrequired to remove such oils and adhesives from the surface. Still,cleaning by organic solvents does not provide enough adhesiveness withthe coating layer and treatment by acids tends to change theinterference color by damaging the oxide film. In comparison, saidtreatment by alkaline solutions does not affect the interference colorwhile preserving adequate adhesiveness with the coating layer.

The transparent coating layer can be formed by applying clear coating ofeither organic or inorganic substances. Publicly known substances,depending on applications, include polyester, polyethylene,polyurethane, polyamide, polyimide, polyvinyl, vinyl chloride, vinylacetate, acrylic resin, epoxy resin, melamine resin, phenol resin,ketone resin, urea resin, fluororesin, silicone resin and copolymersthereof, water glass, alumina, silica, zirconia and other ceramics.Several organic and inorganic substances can be blended. Selectedsubstances can be applied in any form suited for the application.Examples include organic solvent coating, water-based coating, colloidaldispersion coating, powder coating, electrodeposition coating,thermosetting coating and room-temperature drying coating.

The transparent coating layer may also consist of an adhesive or atackiness agent selected from publicly known organic and inorganicsubstances depending on the application. For example, organic substancesinclude polyethylene, polypropylene, polyisobutylene, polyvinyl butyral,vinyl acetate, vinyl chloride, acryls, methacryls, polystylene,polyamide, alkyds, cellulose, cyanoacrylate, polyester, polyurethane,phenoxy, polysulfone, polyacrylsulfone, phenol, resorcinol, urea,melamine, furan, epoxy, isocyanate, silicone, diester acrylate,styrene-butadiene rubber, butyl rubber, polychloroprene, nitrile rubber,polysulfide, polyimide, polybenzimidazole and copolymers thereof.Natural substances include dextrine, soybean protein, albumin, rosin,shellac, gilsonite and casein. Organic substances include water glass,and colloids of alumina, silica and zirconia dispersed in water. Severalorganic and inorganic substances may also be blended depending on theapplication.

A transparent film can be layered by way of said adhesive or tackinessagent. In particular, it is preferable to lay a transparent film on topof the tackiness agent that does not harden and, therefore, does notprevent contamination on its own.

The transparent film is not particularly limited and can be selectedfrom publicly known substances suited for the application. Examplesinclude films of polyester, polypropylene, polyvinyliden, polyvinylalcohol, polyethylene, polyamide, vinyl chloride, vinyliden chloride,vinyl acetate and cellophane. Sheets of such hard substances, whetherorganic or inorganic, as glass, acryls, polycarbonate, vinyl chloride,quartz, zirconia and alumina crystals can also be layered. The thicknessof the film need not be greater than 2 mm when layered directly on thetitanium material, except in some special applications. Yet, thetransparent films and sheets layered by way of the adhesive may have athickness of up to approximately 20 cm. Considering the filmability, theminimum thickness can be down to approximately 5 μm. The film can beapplied not only in one layer but also in multiple layers.

The transparent coating layer and film need not be totally colorless andtransparent. If transparent enough to keep the interference colorunimpaired, the transparent coating layer and film can be colored.Matching the color of the coating layer or film and sheet with theinterference color sometimes increases ornamentality.

When an adhesive or a tackiness agent is used, vibration-damping sheetscan be manufactured by inserting an adhesive between two titaniumsheets. Of course, a clear coating, an adhesive, a tackiness agent or atransparent film or sheet can be applied on the outer surface of thetitanium sheets.

The method of clear coating application is not particularly limited butcan be selected from publicly known application methods suited for theapplication. Examples include rolling coating, roller curtain coating,curtain flow, air-spraying, airless spraying, bar coating, doctorblading, electrostatic coating, dipping, brushing and T-die.

The method of adhesive application is not particularly limited but canbe selected, depending on applications, as with clear coating.

The method of laying transparent films and sheets is not particularlylimited but can be selected from publicly known methods. For example,transparent films and sheets can be applied before the adhesive hardens.When the adhesive is of the type that exhibits adhesiveness onapplication of heat, thermocompression bonding can be applied after theadhesive has been precoated and hardened. Thermocompression bonding canbe also applied to an adhesive sheet placed between a titanium materialand a transparent film or sheet.

The transparent film or sheet itself can be layered on the titaniummaterial by thermocompression bonding when the transparent film or sheetis of the type that exhibits adhesiveness on application of heat.

FIG. 2 shows a partial cross-section of a laminated glass according tothis invention. In FIG. 2, reference numerals 1 and 5 denote sheetglasses, 2 and 4 adhesive layers, and 3 a titanium sheet. The sheetglasses are ones used for conventional laminated glass. If the sheetglasses 1 and 5 are transparent, the laminated glass has an appearancethat reflects the color and luster of the titanium sheet when looked atfrom either side. If either of the sheets glasses 1 and 5 istransparent, the appearance of the laminated glass reflects the colorand luster of the titanium sheet only on the side of the transparentglass.

The titanium sheet may have apertures. Laminated glasses are oftenrequired to have not only beautiful appearance but also abilities topermit admittance of light from outside and viewing the outside frominside as with ordinary sheets of glass. If there are openings, thelight of illumination in the evening passing outside therethrough andhas a beautiful appearance. The amount of sunlight or other transmittedlight can be adjusted by changing the opening ratio in the titaniumsheet. To achieve such effect, the opening ratio should preferably benot smaller than 1 percent. If the opening ratio is smaller than 1percent, the existence of apertures will probably become meaningless. Ifthe opening ration is greater than 90 percent, the color of the titaniumsheet is not much exploited and, as such, the use of titanium becomesmeaningless. If the sheet size is large, difficult handling or otherproblems will arise. Therefore, an opening ratio not greater than 90percent is preferable.

The method of making apertures is not particularly limited. Examples ofapplicable methods include punching, chemical melting by chemicals,electrochemical melting, an electric drill, a laser, a water cutter,snips, and a metal saw. While any of these methods can be combined,punching is most efficient and preferable. If provision of aperturescauses distortion of the titanium sheet, a leveler can be used asrequired.

The most important object of inserting the titanium sheet according tothis invention is to enhance ornamentality. Therefore, the thickness ofthe titanium sheet, though not particularly limited, need not be greaterthan 2 mm. If the thickness is smaller than 0.1 mm, the titanium sheetmight possibly break when it is punched for provision of apertures, whenit is layered with glass sheet or intermediate film or in otherhandling. Therefore, the preferable thickness is approximately notsmaller than 0.1 mm and not greater than 2 mm. If breaking of thetitanium sheet presents no problem, foil-like sheets thinner than 0.1 mmcan be used.

The adhesive layer is required not only to have a good adhesiveness withglass and titanium sheets but also to have a low ultraviolettransmittance. Titanium oxide is formed on the surface of the titaniumsheet. Titanium oxide is known to have a photocatalytic effect. Thelaminated glasses of this invention that have an excellent ornamentalityare often used outdoors where they are directly exposed to the sunlight. On such occasions, the photocatalytic effect of titanium oxidemay possibly decompose the adhesive layer. With titanium oxide of theanatase type having a particularly high photocatalytic effect, there isa possibility that photocatalytic reaction proceeds when exposed tolight with wavelengths not longer than 388 nm. Therefore, light withwavelengths not longer than that must be cut off. Of the light of thesun with wavelengths not longer than 388 nm, however, most withwavelengths under 100 nm is absorbed before reaching the ground.Accordingly, it is enough for the adhesive layer to cut off light ofwavelengths not shorter than 100 nm and not longer than 390 nm. To bemore specific, the transmittance of the light in said wavelength rangeis preferably not higher than 1 percent.

While two-part or photo-setting adhesives can be used for the laminatedglass, hot-melt adhesives are easy to handle and are preferable.Hot-melt adhesives cross-linking on application of heat above a certaintemperature are more preferable because of durability. Of the adhesivesmentioned earlier, ethylene-vinyl acetate copolymer, ethylene-vinylacetate alcohol copolymer, ethylene-methyl methacrylate copolymer,polyvinylbutyl, and polyurethane are usable. Particularly,ethylene-vinyl acetate copolymer is preferable and a thermosetting resinprepared by blending ethylene-vinyl acetate copolymer with organicperoxide is more preferable.

The form of adhesives is not particularly limited. Adhesives in sheet,powder, or paste form can be used.

Though varying with the condition of the sheet glasses and titaniumsheet inserted therebetween and the object of application, the thicknessof the sheet-form adhesive is preferably between approximately 0.1 and2.0 mm. Several sheets of adhesive can be layered to obtain the desiredthickness.

If the titanium sheet deforms because of the roughness of the glass ortitanium sheet or provision of openings in the titanium sheet, theadhesive must be thick enough to cover the deformation.

Either one side or both sides of the sheet-form adhesive can be embossedto a depth of approximately 1 to 50 μm.

Regardless of the form of the adhesive, one acting as a spacer can beused to eliminate thickness variation that might occur inthermo-compression bonding.

The thickness of sheet glasses is not particularly limited and anyappropriate one suited for the application can be chosen. Sheet glassesof thickness between approximately 2 and 25 mm are readily available andpreferable. If any greater thickness is required, multiple sheet glassescan be layered together via adhesive layer. Even when the requiredthickness is smaller than 25 mm, thinner sheet glasses can be layeredvia adhesive layer to increase impact resistance.

The sheet glasses and adhesive layers need not be colorless andtransparent. The sheet glasses and adhesive layers can be colored solong as transparency is large enough not to impair the color of thetitanium sheet. Combining the color of the titanium sheet and that ofthe sheet glass and adhesive layer sometimes increases ornamentality.

In the present invention, the thickness of the film formed by anodicoxidation and that of the alkali titanate layer were determined by Augerelectron spectroscopy. The thickness of the oxide film can be determinedby also multiplying the sputtering time t required until the oxygenconcentration decreases to the intermediate concentration between themaximum and base concentrations by the sputtering speed (oxide filmthickness=sputtering time t×sputtering speed) as shown in FIG. 1 (Depthprofile of oxygen concentration). The thickness of the alkali titanatelayer was also determined by considering the alkali components (such asNa) in the same manner as in determining the thickness of the oxidefilm. The sputtering speed was converted from the speed at which SiO₂was sputtered under the sputtering conditions used in measuring. Theanalysis described above was made under the conditions and by the methoddescribed below.

[Analysis Conditions]

Analysis equipment: PHI 610 scanning Auger electron spectroscope

-   -   (manufactured by Perkin Elmer)    -   Primary electron: 5 kV-100 nA    -   Analysis area: approximately 20 μm×30 μm    -   Sputtering: Ar 2 kV-25 mA    -   Sputtering speed: Approximately 15 nm/min (converted for SiO₂)

[Analysis Method]

After first making a qualitative analysis of the outermost surface bywide scanning, depth composition analysis was made for the elementsfound by the qualitative analysis. To confirm the present elements, widescanning was also conducted during the depth analysis,

EXAMPLES Examples 1 to 7

The titanium sheets used had a thickness of 0.4 mm and anodic oxidefilms of thirteen different thicknesses between 45 and 645 nm formed byapplying constant voltage electrolysis in a 1 mass percent solution ofphosphoric acid with a cathode of SUS 304 stainless steel. After colordevelopment, the titanium sheets had been covered with a protective film(with an adhesive consisting mainly of acryl) and preserved.

The alkali solution was prepared by dissolving a chemical containingcarbonate, silicate, phosphate, nitrite, condensed phosphate,bicarbonate and surfactant, such as FC-L-4480 manufactured by NihonParkerizing Co., Ltd., so that the solid content in 1 liter of watershould become 20 g. The pH of the solution at 60° C. was 11 to 12.

The titanium sheets were dipped in said alkali solution kept at 60° C.for 3 minutes, washed in ion-exchanged water and dried by air blowing atroom temperature.

[Comparison of Interference Colors Before and After Provision of CoatingLayer]

To determine the change in interference color by the provision of acoating layer on the surface, polyester resin was applied by bar coatingto a thickness of approximately 2 μm on the surface of titanium sheetshaving anodic oxide films of 45 to 645 nm in thickness and the colorsbefore and after application were compared. The colors were measured byusing the L*a*b* calorimetric system based on JIS Z 8730 and determinedby visual observation.

Table 1 compares the film thicknesses, color developing mechanisms, L*1values, color differences ΔE and results of determination by visualobservation of the examples according to the present invention andexamples for comparison. For the color developing mechanism, the casesin which the interference color due to the anodic oxide film isstrengthened only at the wavelength corresponding to the color developedby interference, in which the interference color due to the anodic oxidefilm is weakened only at the wavelength corresponding to thecomplementary color of the developed color, or in which the color phasesof the colors due to the wavelengths strengthened and weakened byinterference are as close to each as not more than 90 degrees apart onthe color wheel are designated by ×. The case in which the interferencecolor due to the anodic oxide film is developed by the actions of bothwavelengths strengthened and weakened by interference and the colorphases of the colors due to the wavelengths strengthened and that of thecomplementary colors of the color weakened by interference are as closeto each as not more than 90 degrees apart on the color wheel aredesignated by ◯. For the L*1 value, ◯ designates 33 and above and ×designates under 33. For the color differences ΔE, which was obtainedfrom equation ΔE={(L*2−L*1)²+(a*2−a*1)²+(b*2−b*1)²}^((1/2)), ◯designates under 2.5, Δ not less than 2.5 and under 5, and × over 5.Here, L*1, a*1 and b*1 are the values measured before coating while L*2,a*2 and b*2 are the values measured after coating. Regarding thedetermination by visual observation, ◯ designates the case in which theinterference color remained high enough to preserve good ornamentalityand × designates the case in which the interference color was impairedto such a level as to lose good ornamentality or the surface colorchanged to gray. TABLE 1 Film Color Determination thickness/ developingby visual nm mechanism L*1 ΔE observation Example for 45.0 X X Δ Xcomparison 1 Example for 54.0 X X X X comparison 2 Example for 56.0 X XX X comparison 3 Example for 63.0 X X X X comparison 4 Example for 99.0X X X X comparison 5 Example of the 152.0 ◯ ◯ Δ ◯ invention 1 Example ofthe 225.0 ◯ ◯ ◯ ◯ invention 2 Example of the 238.5 ◯ ◯ ◯ ◯ invention 3Example of the 252.0 ◯ ◯ ◯ ◯ invention 4 Example of the 261.0 ◯ ◯ ◯ ◯invention 5 Example of the 387.0 ◯ ◯ ◯ ◯ invention 6 Example of the585.0 ◯ ◯ ◯ ◯ invention 7 Example for 645.0 No interference ◯ ◯ Xcomparison 6 color

The results show that the anodic oxide films under 150 nm in thicknesslose interference color on application of clear coating while those 150nm or above in thickness retain interference color even afterapplication of color coating. It is also obvious that thicker anodicoxide films are more preferable. When the thickness of the anodic oxidefilm is greater than 600 nm as in the example for comparison 6, however,no vivid interference color is discernible even before the coating layeris formed on the surface. This is because, when the thickness of theanodic oxide film exceeds 600 nm, five or more wavelengths strengthenedand weakened by interference exist in the wavelength range of 400 to 760nm that corresponds to relatively vivid colors and cancel the effects ofthe individual wavelengths.

When the thickness of the anodic oxide film was greater than 600 nm, theoriginal color itself was grayish because the color developing mechanismdue to interference did not work.

Regarding the color developing mechanism, application of clear coatingremoves the interference color when only the wavelength corresponding tothe color developed by interference is strengthened, or when only thewavelength corresponding to the complementary color of the developedcolor is weakened, or when the color phases of the color correspondingto the wavelength strengthened by interference and the colorcorresponding to the wavelength weakened by interference are as close asnot more than 90 degrees away from each other on the color wheel. When,however, the interference color is developed by the actions of bothwavelengths strengthened and weakened by interference and the colorphases of the color developed by the wavelength strengthened byinterference and that of complementary colors of the color developed bythe wavelength weakened by interference are as close to each other asnot more than 90 degrees apart on the color wheel, the interferencecolor remains unremoved even on application of clear coating.

While application of clear coating removes the interference color whenthe L*1 value is under 33, the interference color remains unremoved whenthe L*1 value is 33 or above.

[Method for Manufacturing Laminated Glass]

Example 8

The sheet glass was an ordinary 6 mm thick sodium-calcium silicateglass. The sheet-form adhesive was a 0.45 mm thick adhesive consistingmainly of ethylene-vinyl acetate copolymer. The titanium sheet was a 0.4mm thick sheet that had been preserved with a protective film (with anadhesive consisting mainly of acryl) on the surface. After removing theprotective film, the titanium sheet was subjected to a treatment in analkali solution as in the case of Examples 1 to 7. Then, a laminatedglass having an interposed titanium sheet was prepared by layeringtogether sheet glasses 6 and 10, sheet-form adhesives 7 and 9 andtitanium sheet 8, as shown in FIG. 3, and applying thermo-compressionbonding with a pressure of 5 kg/cm² and at a temperature of 130° C. byusing a hot press. The sheet glass and titanium sheet were bondedtogether with good adhesiveness. In addition, the laminated glass had ahigh ornamentality reflecting the unique appearance of the interposedtitanium sheet, without being affected by the object behind thelaminated glass, as shown in FIG. 4.

Example 9

FIG. 5 shows an example of the laminated glass interposed with atitanium sheet having openings. The openings in the interposed titaniumsheet were made by punching. The laminated glass of Example 9, unlikethat of Example 8, permits seeing the object therebehind through theopenings. This feature permits the laminated glass to be used forwindows. Also, the laminated glass had a high ornamentality reflectingthe unique appearance of the interposed titanium sheet. Adequateadhesiveness was achieved without impairing the bonding with the sheetglasses despite the presence of the openings in the titanium sheet.

In manufacturing the laminated glass interposed with the titanium sheethaving openings, the titanium sheet was punched to form the openingswithout removing the protective film. After then removing the protectivefilm, the titanium sheet was subjected to degreasing in alkali andthermo-compression bonding under the same condition as for Example 8.

[Comparison of Colors Before and After Glass Laminating]

Examples 10 to 16

Titanium sheets having anode oxide films 45 to 645 nm in thickness werethermo-compression bonded to sheet glasses via adhesive layers in thesame way as Example 8. The anodic oxide films on the titanium sheetswere formed by applying constant voltage electrolysis to a 1 masspercent solution of phosphoric acid, with the cathode of SUS 304stainless steel.

To determine the changes in color before and after application of glasslamination, measurement of the L*a*b* colorimetric system based on JIS Z8730 and confirmation of color by visual observation were made.

Table 2 compares the film thicknesses, color developing mechanisms, L*1values, color differences ΔE and results of determination by visualobservation of the examples. Here, the color developing mechanisms areclassified into:

-   -   1. The cases in which the interference color due to the anodic        oxide film is strengthened only at the wavelength corresponding        to the color developed by interference, in which the        interference color due to the anodic oxide film is weakened only        at the wavelength corresponding to the complementary color of        the developed color, or in which the color phases of the color        developed by the wavelength strengthened by interference and        that of complementary colors of the color developed by the        wavelength weakened by interference are as close to each as not        more than 90 degrees apart on the color wheel.    -   2. The case in which the interference color due to the anodic        oxide film is developed by the actions of both wavelengths        strengthened and weakened by interference and the color phases        of the color developed by the wavelength the strengthened by        interference and that of complementary colors of the color        developed by the wavelength weakened by interference are as        close to each as not more than 90 degrees apart on the color        wheel.    -   3. The case in which five or more wavelengths strengthened and        weakened by interference exist in the visible light wavelength        range of 400 to 760 nm corresponding to relatively vivid colors.

While the high lightness L*1 is not lower than 33, the low lightness L*1is under 33.

The color differences ΔE, which was obtained from equationΔE={(L*2−L*1)²+(a*2−a*1)²+(b*2−b*1)²}^(1/2). The small difference wasunder 2.5, the medium difference was not lower than 2.5 and under 5, andthe large difference was over 5. Here, L*1, a*1 and b*1 are the valuesmeasured before bonding while L*2, a*2 and b*2 are the values measuredafter bonding. Regarding the results of visual observation, C designatesthe vivid color development by interference and G designates the colorchanged to gray. TABLE 2 Film Color Determination thick- developing byvisual ness/nm mechanism L*1 ΔE observation Example for 45.0 1 LowMedium G comparison 7 Example for 54.0 1 Low Large G comparison 8Example for 56.0 1 Low Large G comparison 9 Example for 63.0 1 Low LargeG comparison 10 Example for 99.0 1 Low Large G comparison 11 Example ofthe 152.0 2 High Medium C invention 10 Example of the 225.0 2 High SmallC invention 11 Example of the 238.5 2 High Small C invention 12 Exampleof the 252.0 2 High Small C invention 13 Example of the 261.0 2 HighSmall C invention 14 Example of the 387.0 2 High Small C invention 15Example of the 585.0 2 High Small C invention 16 Example for 645.0 3High Small —* comparison 12*This example was not evaluated because the color thereof was silvergray before glass lamination, with no interference color.

The results show that laminated glasses exploiting the interferencecolor can be obtained by using titanium sheets with anodic oxide filmsnot less than 150 nm and not more than 600 nm in thickness. The anodicoxide film thicknesses not less than 200 nm and nor more than 600 nm aremore preferable.

Regarding the color developing mechanism, the preferable titanium sheetsare those whose interference color is developed by the action of bothwavelengths strengthened and weakened by interference, with thecomplementary colors of the color developed by the wavelengthstrengthened by interference and that of the color developed by thewavelength weakened by interference as close to each other as not morethan 90 degrees apart on the color wheel. The preferable lightness L* isnot lower than 33. [Changes in Adhesiveness between Titanium Sheet andSheet-Form Adhesive Caused by Alkali Treatment]

Examples 17 to 19

Three titanium sheets having an anodic oxide film with a thickness of225 mm were, after removing the protective film, left untreated,ultrasonically cleaned for 3 minutes in MEK (methyl ethyl ketone) atroom temperature, and in said alkali solution under said conditions.Analysis by the Auger spectroscopy showed no difference between theuntreated and MEK cleaned titanium sheets. The titanium sheet treated inthe alkali solution showed Na that was scarcely found in the untreatedsheet. Depthwise analysis by said method showed that the Naconcentration at a depth of 3 nm from the outermost surface wasintermediate between the base concentration in the oxide film and themaximum concentration. This showed that the alkali titanate layer formedon the anodic oxide film had a thickness of 3 nm.

To determine the adhesiveness between said three titanium sheets and thesheet-form adhesive, 610 mm square laminated glass specimens wereprepared by the preparation method described earlier and a falling balltest was conducted. Table 3 shows the results of the test conducted bydropping a steel ball weighing 1040±10 g from a height of 240 cm.Because the test was not conducted to evaluate the adhesiveness betweenthe glass and sheet-form adhesive, evaluation was made on the followingunique criteria. ◯ denotes that the titanium sheet and adhesive layerstuck closely to each other, with no peeling. A denotes that thetitanium sheet and adhesive layer did not stick co closely, with thepartial peeling therebetween accounting for less than 30 percent of thewhole area. × denotes that the titanium sheet and adhesive layer stuckpoorly, with the peeling therebetween accounting for 30 percent or moreof the whole area. TABLE 3 Method of treatment N = 1 N = 2 N = 3 N = 4 N= 5 Example of the Alkali ◯ ◯ ◯ ◯ ◯ invention 17 treatment Example ofthe Untreated Δ Δ Δ Δ Δ invention 18 Example of the MEK cleaning Δ ◯ Δ Δ◯ invention 19

Obviously, the titanium sheet treated in alkali solution proved to havegreater adhesion with the adhesive layer than the titanium sheetsuntreated or cleaned in MEK.

Industrial Applicability

This invention permits protecting the surface of titanium sheets whileleaving the interference color thereof developed by interference byapplying simple and inexpensive treatment without necessitating anysubstantial equipment revamping. This, in turn, permits using materialsfor buildings, household electrical appliances, furniture and varioussmall articles exploiting the interference color of titanium overprolonged periods without requiring repairs. This invention also makesit possible to manufacture titanium-interposed laminated glasses havinghigh ornamentality and exploiting the interference color of titanium,that can be used as building materials.

1. A titanium material having an oxide film with an interference colorformed on the surface thereof and covered with a transparent coatinglayer, characterized in that said oxide film has a thickness of 150 to600 mm.
 2. A titanium material having an oxide film with an interferencecolor formed on the surface thereof whose interference color isdeveloped by the action of a wavelength strengthened by interference anda wavelength weakened by interference and covered with a transparentcoating layer, characterized in that the color phases of the colordeveloped by the wavelength strengthened by interference and that ofcomplementary colors of the color developed by the wavelength weakenedby interference are as close to each other as not more than 90 degreesapart on the color wheel.
 3. A titanium material having a coating layeron the surface thereof according to claim 1, characterized in that thecolor phases of the color developed by the wavelength strengthened byinterference and that of complementary colors of the color developed bythe wavelength weakened by interference are as close to each other asnot more than 90 degrees apart on the color wheel.
 4. A titaniummaterial having a coating layer on the surface thereof, characterized inthat the titanium material whose lightness in color before the formationof the coating layer is not less than 33 in terms of the L* value on theL*a*b* calorimetric system based on JIS Z
 8730. 5. A titanium materialhaving a coating layer on the surface thereof according to claim 1,characterized in that the titanium material whose lightness in colorbefore the formation of the coating layer is not less than 33 in termsof the L* value on the L*a*b* calorimetric system based on JIS Z 8730.6. A titanium material having a coating layer on the surface thereofaccording to claim 1, characterized in that said oxide film is coveredwith an alkali titanate layer.
 7. (canceled)
 8. A titanium materialhaving a coating layer on the surface thereof according to claim 1,characterized in that said transparent coating layer is a clear paintfilm.
 9. A titanium material having a coating layer on the surfacethereof according to claim 1, characterized in that said transparentcoating layer is a layer of adhesive.
 10. A laminated glass comprisingmultiple sheet glasses layered together by means of an adhesive layer inwhich the titanium material according to claim 1 is interlayered betweensaid sheet glasses by way of said layers of adhesive.
 11. A laminatedglass according to claim 10 in which said titanium materials haveopenings of 1 to 90 percent in said titanium materials.
 12. A laminatedglass according to claim 10 in which the light transmittance of saidlayer of adhesive at the wavelength between 100 and 390 nm is notgreater than 1 percent.
 13. A laminated glass according to claim 10 inwhich said layer of adhesive is a hot melt adhesive.
 14. A method formanufacturing the titanium material having a coating layer on thesurface thereof according to claim 1 comprising the steps of forming anoxide film on the surface of a titanium material, treating in analkaline solution, and covering the surface with a transparent coatinglayer.
 15. A method for manufacturing the titanium material having acoating layer on the surface thereof according to claim 14 in which thepH of said alkaline solution is not lower than 8 and not higher than 14and the treatment temperature is not lower than 10° C. and not higherthan 90° C.
 16. A method for manufacturing the laminated glass accordingto claim 10 comprising the steps of forming an oxide film on the surfaceof a titanium sheet, treating in an alkaline solution, and laminationthe titanium sheet and sheet glasses through an adhesive layer.
 17. Amethod for manufacturing the laminated glass according to claim 16 inwhich the pH of said alkaline solution is not lower than 8 and nothigher than 14 and the treatment temperature is not lower than 10° C.and not higher than 90° C.
 18. A method for manufacturing the laminatedglass according to claim 16 in which the layer of adhesive issheet-formed and the sheet glasses, sheet-formed adhesive and titaniumsheet are layered together in the desired order and laminated togetherby hot press lamination.